In general, when a vibration generating body, such as an engine, is mounted on a vibration receiving body, such as a vehicle body, a vibration control equipment is interposed between the vibration generating body and the vibration receiving body so as to prevent or suppress vibration from being transmitted from the vibration generating body to the vibration receiving body. As such a vibration control equipment, there is a sandwich-type vibration control equipment including a pair of damping rubbers and plate members placed on both sides of the damping rubbers. Each of the damping rubbers is composed of an outer tube formed substantially in the shape of a cylinder and has a flange portion formed at an axial outer end portion, an inner tube substantially in the shape of a cylinder disposed in the inside of the outer tube, and a rubber elastic body interposed between the outer tube and the inner tube. The pair of damping rubbers is connected to each other by abutting the axial inner ends thereof, so that the damping rubbers are axially clamped at the outside thereof by means of the pair of plate members. Also, the pair of plate members is connected to each other by means of fastening members, such as bolts, penetrating through the inside of the pair of inner tubes (e.g., see Patent Document 1).
With the sandwich-type vibration control equipment constructed as described above, as the stiffness of the damping rubber is lowered, the vibration-resistance properties are enhanced. However, there is a problem that if the support rigidity of the damping rubbers is lowered too much, the vibration generating body interferes with surrounding objects. Consequently, a technique of forming mold cavity portions in a rubber elastic body has been proposed in order to improve the vibration-resistance properties of the damping rubbers, as well as ensuring the support rigidity of the damping rubbers. In the damping rubber having the mold cavity portions, since the rigidity is lowered only in the arranging direction of the mold cavity portions, the vibration-resistance performance thereof is different in the vibration input direction. According to this technique, since the rigidity in the direction of the vibration transmitted from the vibration generating body can be set lower, it can ensure the support rigidity and thus improve the vibration-resistance properties (e.g., see Patent Document 2).
For example, in the case where the vibration control equipment is installed on the vehicle body through a bracket member and the plate member of the vibration control equipment is fixed to a lower portion of the engine, the vibration transmitted from the engine to the vibration control equipment causes rolling vibration to be generated around a driving shaft of the engine. In this instance, the mold cavity portions are disposed in a planar rolling direction, that is, a right and left direction (a horizontal direction perpendicular to an engine shaft), so that the damping rubbers are positioned in a circumferential direction. This will help to ensure the support rigidity and improve the vibration-resistance properties, while the rigidity is maintained intact in an upward and downward direction (an axial direction of the damping rubbers) and a front and rear direction (a direction in parallel with the engine shaft) but the rigidity is lowered in the left and right direction.    [Patent Document 1] Japanese Unexamined Utility Model Application, First Publication No. 559-191452    [Patent Document 2] Japanese Unexamined Patent Application, First Publication No. 2000-193003